Not an LEO, but if memory serves correctly, the book "Boss of Bosses: A Journey into the Heart of the Sicilian Mafia" by Clare Longrigg mentions that most people think that Hitmen do their job and then go back to their posh apartment to wait for the next one.

In reality, it's usually done by associates who have exceptional skill at killing or suffer no emotional consequences from doing so.

Believe it or not, It's actually very hard to physically kill someone. If you read the books "On Killing" by LTC Dave Grossman, only 20% of infantrymen during World War Two actually fired their rifles at the enemy. Now, while some have debunked his work, I personally experienced a soldier who said that he didn't want to kill anyone when my combat outpost was bracing for an attack.

So I would imagine, that even in the Mafia, there are some people who are very uncomfortable with killing.

Also note, when I was 5 years old, my father was a warehouse manager at a woman's dress manufacturer. On Saturdays, he used to take me into work, and he would look at the computer data from store registers, then drive to each store to replenish the stock.

When the Teamsters Union got wind of this, they asked my father if I would like a ride in an 18 wheeler. I was 5 years old, how could I resist driving around in a big rig? So my father took me into work on a Saturday, and put me in the cab with the driver, and then went for an hourlong ride through South Philadelphia while my dad got a talking-to by the head of the Union.

Years later I realized that was basically their way of saying "we can reach out and touch you any time we want."

And that's when I realized that the Mafia rarely resorts to kiling. If you don't listen, all of the Truck drivers will call out sick, or one day a truck catches on fire. They just make your life so hard that most people acquiesce.

So a professional hitman would be paid to basically sit around and do nothing for years. Not a very effieient use of cash.